#border-top-color
Like border-color, but for the top border only.
border-top-color: transparent;
Applies a transparent color to the top border. The top border will still take up the space defined by the border-width value.
border-top-color: red;
You can use one of the 140+ color names.
border-top-color: #05ffb0;
You can use hexadecimal color codes, rgb(), rgba(), hsl(), hsla()...